Historically in high speed rotating shaft environments the use of screw pumps have proven to be reliable oil pumps when the screw pumps have been primed. Priming has presented a problem if the pumping has to be accomplished against a head of several inches. In the past this matter of priming has been handled by the addition of a capillary tube in an attempt to maintain the oil height at the screw thread regardless of the oil level in the housing that carries the high speed rotating shaft.
Typically the prior art lubrication system has included a wick that extends from a source of lubricant into contact with the rotating shaft of the assembly sought to be lubricated. The wick, screw pump and capillary volume was sealed using a labyrinth seal on the shaft. In order for the screw pump and capillary to function, the screw pump and capillary must be matched to accomplish the desired flow. The oil rise as a result of capillary action occurs at zero flow and is a result of the equilibrium between the vertical upward component of the surface tension and the weight of the oil in the capillary. Experience has revealed capillaries will typically provide a rise of about 1.25 inches minimum. In typical arrangements of this nature, in order to achieve desired flow, capillaries in parallel are required. This type of arangement is essentially unstable, unpredictable and susceptible to such factors as is assembly set up, oil viscosities and static inlet head. The invention to be described more fully hereinafter completely avoids the requirement for capillaries and the attendant problems just noted. U.S. Pat. No. 2,916,890 to C. R. Stien illustrates the wick type of lubrication system.
The patent to DeLisse, U.S. Pat. No. 3,618,710 is directed to a metering and scavenging pump wherein the lubrication system comprises a reservoir having a feed tube 26 which delivers lubricant to a pump 38 which may be of the screw pump type. The DeLisse patent however, provides no teaching of a lubrication system of the type to be described in respect of the subject invention where lubricant is delivered via a conduit to a control region where a pair of oppositely threaded portions of a shaft deliver oil to spring loaded bearings via sleeves mounted concentric to the shaft. Each of the bearings are on either side of the central region bearings.
The invention to be described hereinafter recognizes that opposed threaded portions on a shaft to deliver lubricant from a pair of opposite regions of a single sleeve bearing is basically old; for this is shown in British Pat. No. 694,910. The British Patent stores lubricant in a wick 32. Another patent of interest is that of Lindt et al, U.S. Pat. No. 3,243,241 which covers the idea of delivering lubricant from a central region to a bearing. Note in FIG. 1 of Lindt et al, that oil pumping groove 23 delivers lubricant from a lubricant storage wick 32 to a bearing 8. The prior art just reviewed does not show the inventive arrangement set forth in the specification that follows.